The present invention relates generally to spray tips or nozzles for use in spray guns which are adapted to hydraulically atomize and spray liquids such as paint, and particularly to such spray tips or nozzles wherein the spray tip is reversible so that obstructions therein which clog the nozzle may be easily removed by the reversed flow of the high pressure liquid therethrough. More particularly, the invention relates to such nozzles that can be disassembled without tools.
An inherent disadvantage in hydraulic or airless spray painting, wherein paint under high pressure is supplied to a spray gun and forced through a spray tip or nozzle, is clogging. Because of the nature of this method of paint spraying, it is necessary that the spray opening in the spray tip be very small so that as the paint reaches the spray tip under high pressure and low velocity, it is accelerated through the spray opening to a high velocity and low pressure thereby forming a fan spray suitable for painting. Because of the small size of the spray opening, the spray is susceptible to clogging with particles carried in the fluid paint.
One simple method of unclogging hydraulic spray tips is to provide a spray tip which is reversible so that the flow therethrough can be reversed to thereby dislodge the particles causing the clog. Examples of hydraulic spray tips incorporating such reversibility can be found in U.S. Pat. No. 4,508,268, to Geberth, Jr., granted Apr. 2, 1985; U.S. Pat. No. 3,202,360, to O'Brien, granted Aug. 24, 1965; U.S. Pat. No. 4,165,836, to Eull, granted Aug. 28, 1979; U.S. Pat. No. 4,715,537, to Calder, granted Dec. 29, 1987; and U.S. Pat. No. 4,830,281 to Calder, granted May 16, 1989.
In each of these prior art patents, the spray tip is mounted in a diametric passageway in a transverse cylinder which is adapted for axial rotation so as to present the spray tip forwardly for spraying or rearwardly so that the spray tip faces the high pressure liquid. In the latter position, the high pressure liquid passing through the spray tip in the reversed direction dislodges and removes any clogging matter therein. The transverse, axially rotatable cylinder is supported in a transverse passageway of a housing which has a flange at its end facing the discharge end of the spray gun, which flange is engaged by a securing nut which secures the assembly to the forward end of the spray gun. Sealing members are also provided to prevent leakage during operation of the spray tip.
A major problem inherent in such reversible spray tips is preventing leakage between the axially rotatable cylindrical member and the fluid passageway passing through the housing delivering the high pressure fluid paint to the spray opening of the spray tip. The usual construction of such reversible spray tips includes an insert axially arranged in an axial passageway of the housing and which is provided with a fluid passageway passing therethrough. This insert performs the sealing function and is formed of a generally soft material such as plastic with a flange at the end facing the spray gun which is compressed between the flange of the housing and the discharge end of the spray gun. The end of the insert facing the rotatable cylinder may be formed of plastic material as in U.S. Pat. No. 4,508,268 or it may be provided with a hard material at this face as disclosed in U.S. Pat. No. 4,611,758, to Geberth, Jr., granted Sep. 16, 1986. In either event, sealing pressure is provided by the securing nut which must be tightened significantly.
Another problem occurs after spraying with the nozzle, when it is desirable to disassemble the nozzle for cleaning. The seal insert may become lodged in the axial passageway of the housing, and the insert is sometimes difficult to remove, requiring the use of a tool to eject the seal insert. U.S. Pat. No. 4,830,281 sizes a turret member for use as an ejector pin to remove a seal insert. However, the turret member is a finely machined part, and using the turret member to eject the seal insert can scratch or mar the machined surface or damage the seal insert, either of which can adversely affect the sealing function between the seal insert and the turret member during spraying operations. Moreover, a preferred axial passageway for receiving the seal insert is rectangular to ensure proper alignment of the seal insert. However, a rectangular passageway poses an additional problem in that a cylindrical turret member does not match a rectangular opening.
Moreover, if the cylindrical turret member is used to dislodge the seal from the housing, paint may drip from the guards onto the cylindrical turret portion. This is a problem in that the turret member should be kept clean in order to provide a smooth seal against the insert.